Air conditioning system



1944. R. B. P. CRAWFORD 2,359,624

AIR CONDITIONING SYSTEM Original Filed March 5, 1939 3 Sheets-Sheet l 4R. B. P. CRAWFORD ,35

AIR CONDITIONING SYSTEM Original Filed March 3, 1939 5 Sheets-Sheet 2Invenlror Roloczrl 8.1? Crawfov].

5 Aii -ornqf' 5 1944. R. B. P. CRAWFORD 2,359,624

AIR conmnonme SYSTEM Original Filed March 5, 1939 3 Sheets-Sheet s (IAIII III) IlIIIlII/llllll. nnnnunnnnuIr"In":uIIInuunnnanunuu PatentedOct. 3, 1944 AIR CONDITIONING SYSTEIH Robert B. r. Crawford, Miami,Fla., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis,Minn., a corporation oi Delaware Original application March a, 1939,Serial No.

259,561: Divided and this application December 13, 1941, Serial No.422,829

6 Claims.

This invention relates to air conditioning systems for maintainingdesired air conditions within an enclosure. r

v This application is a division of my previously filed applicationSerial No; 259,561, filed March 3, 1939, now Patent No. 2,286,605.

An object of this invention is to'provide an air conditioning systemhaving two stages of cooling, one primarily for sensible cooling and theother primarily for latent cooling, along with a stage of reheatingwherein the heat dissipated by the reheating stage assists the coolingaction performed by the latent cooling stage;

Another object of this invention is to provide a novel cooling tower fordissipating in a more economical manner the heat absorbed by thecoolingapparatus of an air conditioning system, and particularly wherethe air conditioning system is of the two-stage type with reheat as setforth above.

Another object is to provide a cooling tower having increased efllciencywherein the spray water is introduced at level in the tower where thewet bulb temperature oi, the air is the same as the temperature of thespray water.

Another objectis to provide automatic controls for accomplishing thepreceding object.

Further objects of this invention reside in the structure and sequenceof operation or the air -conditioning system of this inventionl Anotherobject of, this invention is to provide automatic control systems forthe air conditioning system of this invention whereby the sequences ofoperation thereof may be automatically controlled.

ing unit I! and passes progressivelylover a-precooling coil l3, an aftercooling coil I4, and a reheat coil ii. For purposes of illustration itis assumed that outside air is utilized for conditioning Purposes andunder maximum load conditions it is assumed that this outside air has adry bulb temperature of 100, a wet bulb temperature of 80, and adew-point temperature of 72. It

is also assumed that the preco'oling' coil l3.is so selected andconstructed that it cools the air to acondition wherein the dry bulbtemperature '15 65, the wet bulb temperature is 63, and the dewpointtemperature is 62. Further it is assumed thatthe after cooling coil I4is so selected that the air leaving this coil assumes a dry bulb tem:perature'of 60, a wet'bulb temperature of 57 and a dew-point temperatureof 559.. From the above it is seen that the precooling cofl I3 isutilized primarily for sensible cooling and-that the after' cooling coilII is utilized primarily for latent cooling. The reheat coil I5 isassumed to be so selected that the condition of the air leaving the samewill have a dry bulb temperature 01.75, a wet bulb temperature of 625and a dewpoint temperature of 55, In other words, the reheat coil i5sass sensible heat to the air to prevent the dry bulb temperature or theair entering 7 primarily in the form of latent cooling and the Otherobjects and advantag'es'will become apparentto those skilled in-the artupon reference to the accompanying specification, claims and drawings,in which Figure 1 is a diagrammatic illustration oi one form of thisinvention,

Figures), 3, and 4 are diagrammatic illustrations of controlarrangements utilized in Figure 1,

Figure 5 is a diagrammatic illustration of another form of thisinvention, and

Figures 6, 7,3, and 9 are diagrammatic illustra-' designated at l8,cooling water is supplied to the 1 tions of control arrangementsutilized in Figure 5.

Referring now to Figure 1, an enclosure to be air conditioned isdesignated at 10. A fan ll draws air through an air conditioning unitgenerally designated at I! and discharges conditioned air intotheenclosure In for air conditioning purposes. Fresh air, return air, or amixture of fresh air and return air enters the air condition reheatingcoil I5 adds substantially 3,750 B. t. 11. per minute in the form ofsensible heating. In other words, the reheat coil 15 adds sensible heat.

substantially equivalent to the latent heat removed bythe aftercoolingcoil ll. 4 r

Cooling water is supp d t t pr ing c il it from a relatively evaporatorgenerally after cooling coil M from a relatively cold evap-' oratorgenerally designated at IT and re eat t water is supplied to the reheatcoil l5 from a cooling tower generally designated at l8.

The relatively warm evaporator It may coi n prise a chamber 20 in whichcooled water is 001- lected. This cooled water is withdrawn from thechamber 20 through a pipe 2i by a pump 22 and delivered through a pipe23 to the precooling coil l3 and for purposes 01'. illustration it isassource of water (not shown).

returned from the precooling coil l3 through a pipe 24 and a spray 25 tothe evaporator chamber 20 and for purposes of illustrationit is assumedthat the temperature of this water is substantially 85. A multi-stagecentrifugal compressor 21 shown to be of the three stage type isconnected by a pipe 28 to .the evaporator chamber 28- for reducing thepressure in the chamber 28 and for withdrawing vapor from the chamber 28whereby some of the water sprayed from the spray 25 is evaporated tocool the remainder of the water by evaporation. The multi-stagecentrifugal compressor 21 discharges through a pipe 29 into a condenser88 and for purposes of illustration it is assumed that the centrifugalcompressor is so selected and that the condensing temperature in thecondenser 38 is such that the three-stage steam turbine may be ofthesingle stage type or may contain any number of stages. Steam issupplied to the steam turbine 8| through a steam supply line 82 leadingfrom some source of steam (not shown) and the supply of steam to thesteam turbine 3 may be controlled by a motorized valve 38 preferably ofthe proportioning type. The steam turbine 3| discharges. through a pipe84 into a condenser 35.

-Make up water is supplied to the evaporator chamber 28 to make up forthe water lost through evaporation through a'pipe 81 leading from someThesupply of make up water may be controlled by a valve 38 which in turnis controlled by-a float 89 responsive to the level of the water in thechamber 28. The float operated valve 88 therefore maintains the level ofthe water in the chamber 28 at substantially a constant value at alltimes.

The relatively cold. evaporator |I may comprise a chamber 4| for.collecting cold water. This cold water is withdrawn from the chamber 4|through a pipe 42 by a pump 43' and r's dis charged through a pipe 44into the after cooling coil l4 and for purposes of illustration it isassumed that thetemperature of the water supplied to the after coolingcoil I4 is substantially The cooled water returns .from the aftercooling coil l4 through .a pipe 45 and through a spray 46 to theevaporator chamber 4| and'for purposes of illustration it is assumedthat the temperature of this water is substantially It is here notedthat the cooling water is supplied to the cooling coils l8 and I4 at thedown-stream side thereof so that a counter-flow heat exchange betweenthe coolingwater and the air being cooled is obtained. This greatlyincreases the cooling effect of the cooling coils on the air andincreases the spread of the water temperatures;-

A multi-stage centrifugal compressor 48 is connected by a pipe 49 to theevaporator chamber 4| for lowering th pressure therein and forexhausting vapor therefrom so that some of the water emanating from thesprays 48 is evaporated to cool the remaining water. The centrifugalcompressor 48 discharges-through a pipe 58 into a condenser 5|. Forpurposes of illustration it is assumed that the temperature of the con--water is substantially 85.

denser 5| and the construction of the centrifugal compressor 48 are suchthat the water in the evaporator chamber 4| is cooled to a value ofsubstantially 50. The centrifugal compressor 48 is operated by amulti-stage steam turbine 52 receiving a supply of steam through a steampipe 53 leading from some source of steam (not shown). A motorized valve54 preferably of "the proportioning or modulating type regulates thesupply of steam to the steam turbine 52. The steam turbine 52 dischargesthrough a pipe 55 into a condenser 56. Here again, the centrifugalcompressor 48 and the steam turbine 52 are shown to be three-stage unitsbut as pointed out above, these "nits may be of the single stage type ormay have any number of stages. Make up water is supplied to theevaporator chamber 4| througha water pipe 58 under the control of avalve 58 which in turn is controlled by a float 68 to supply water tothe evaporator chamber 4| to make up for water evaporated thereinandhenc to maintain the level of water in the evaporator chamber 4| at asubstantially constant value. v

"The cooling-tower generally'designated at |8 may comprise a verticalchamber 82 provided with air inletopenings 53 near the bottom thereof. Afan 54 draws air, which may b outside air, through the openings 68upwardly through the tower and discharges it to atmosphere. The air asit travels upwardly through the tower is contacted by water sprayed froma plurality of sprays for cooling the water and eliminator plates may beprovided for preventing moisture from passing into the fan 54. Make upwater may be supplied to the lower portion of the cooling tower througha pipe 55 leading from some source of water (not shown) and th supply ofmake up water may be controlled by a valve 81 which in turn iscontrolled by a float 88. The float valve 51 therefore maintains thelevel of the water in the lower part of the cooling tower at asubstantially constant value.

Water is withdrawn from the bottom of the cooling tower l8 through apipe I8 by a pump II and is discharged through pipes 12, I3, 14, and 15,a motorized valve 18 preferably of the proportioning or modulating typeand apipe II to the reheat coil l5 and for purposes of illustration itis assumed that the temperature of this This water gives up heat to theair passing over the reheat coil I5 and in so doing'is cooled to avalue, illustratively 70, and this 70 water is discharged through a pipe18 intoa coil 18 in the condenser 5|. The condensing temperature in thecondenser 5| is therefore substantially 70 which enables the evaporatorI! to produce relatively cool water at substantially 50. I

Water flows from the coil 18 through a pipe 8| into an ejector 82 andcondensed vapor in the condenser 5| is drawn therefrom through a pipe 83by a pump 84 and is discharged into the ejector 82 by a pipe 85. Theejector 82 therefore mixes water leaving the coil 18 and water leavingthe condenser 5| and this water is discharged, illustratively at",through a pipe 86 to one of a plurality of sprays 81, 88 and 88 locatedin the cooling tower l8. Solenoid valves 90; 8|, and 92: determine whichspray shall be operated to spray the water into the cooling tower I8.For reasons to be pointed out more fully hereafter, it is desirable tospray the water into the tower at a point where the temperature of thewater corresponds substantially to the wet 2,859,824 bulb temperature ofthe air rising upwardly throughthe cooling tower at the point at whichit is admitted- For example, if the temperature of the water issubstantially 90, as illustrated, and the wet bulb temperature or theair just above the spray 89 is substantially 90 then the valve 92 isoperated to cause the spray 89 to becomeoperative to spr'ay water intothe cooling tower I8. If on the other hand the wet bulb temperature oftheair just above the spray 88 should be substantially 90 then the spray88 would become operative to spray water into the cooling tower. Also ifthe wet bulb temperature of the air. just above the spray 88 should be,'saythe wet bulb temperature of the air rising through the tower I8, thearrangement being such that the temperature of the. water and the wetbulb temperature of the air substantially coincide at Th same operationholds true ditions should become extremely severe so that all of thevalves I I8, I I9, and I 28 should be closed then the water passesthrough a pressure relief valve I2I into the upper spray H1 or into anfrom the steam turbine 52. Water flows from the coil I28 through a pipeI21 into an ejector I28 and condenser steam is withdrawn from theconthepoint of entry of thewater into the cooling tower. If under severeload conditions all of the valves 98, 9|, and 92 should be closed thenAccordingly the condensing temperature of the condenser 88 issubstantially 85 andtherefore the evaporator I8 operating at a highercondens- I ing temperature cools the water to only as illustrated. Wateris discharged from the coil 98 through a pipe 81 into an ejector 98 andcondensed vapor is withdrawn fromth condenser 88 by a pump 98 and isdischarged through a pipe I88 into the ejector 88. .Accordingly theejector 98 mixes the water leaving the coil 98" and the condensed vaporleaving the condenser 88 and this water is discharged at'illustratively..95 through pipe I8I to a spray I82 located in the cooling tower I8above the sprays 81, 88, and 89. I

Water from the cooling tower I8 at 85 is also supplied by the pump 1Ithrough pipes 12 and I85 to acoil I88 located in the condenser 85 andwater is discharged from the coil I88 through acondensing-water and thecondensed steam'ar'e additional spray (not shown) located above thespray II1.

Water at illustratively 85 is supplied from the cooling tower I8 by pump1| through pipes 12,

18, I4, and I into a coil I26 located in the con-' denser 58 forcondensing the steam discharged denser 58 through a pipe I29 by a pumpI30 and is discharged through a'pipe I3I into the ejector I28. Thcondensed water and the condensed steam are therefore mixed in theejector I28 and this mixture at illustratively 115 passes through pipesI32 andI M into one or the sprays II5, I I8, and H1.

In addition to evacuating condensate from the condensers 88, 35, 5|, and58 air, must also be evacuated therefrom to maintain desired. vacuumconditions therein. This may be accomplished in any well known mannereither by providing separate air evacuators, not shown, or byconstructing the pumps 99, H8, 84, and I38 so that they will remove andvent the air to atmosphere while discharging the condensate to-theirrespective electors.

1 The motorized steam valve 33 which controls the supply of steam to thesteam turbine 3| and hence which controls the evacuation of theevaporator I8 and the temperature of the water therein may becontrol-led by a temperature responsive controller I38 responsiveto thetemperature within the enclosure III, a temperature responsivecontroller I31 responsive tothe tem- =perature of the air dischargedfrom the precooling coil I8 and by a liquid level controller I88,responsive to the level of the water in the relatively warm evaporatorI8. The temperature responsive controller I38 operates as the primarycontrol of the steamvalve 83 to position modu-,

latingly the same to'malntain the temperature within the enclosurebetween, illustratlvely, 75

and 85. The temperature responsive controller I81 acts'as a secondary orlimit control for'modulatingly positioning the steam valve 33 to closeoil'- the steam valve if the temperature of th air leaving theprecooling. coil decreases below until such time as the temperaturedecreases to 60 at which time the valve 38 will become completelyclosed. This eflectively prevents the temperature of the precooling coilI3 from becoming too low whereby the precooling coil 13 acts primarilyto remove sensible heat and not latent pipe I81 into an ejector I88.- Apump II8 withdraws condensed steam from the condenser 88 through pipeI89 and discharges this steam. through a pipe III into the ejector I88.The

heat. If for some reason the level ofthe water entering the centrifugalcompressor 21, the liquid 2 level controller I88 will close of! thesteam valve therefore mixed in the ejector-I88 and the mix 4 ture isdischarged, illustratively at 115, through pipes- H8 and Ill into onefof a plurality of sprays H5, H8, and 1 located in the cooling II8,- H9,and I28 determine which spray shall spray this water into the coolingtower I8 and here again, as pointed out above, thegsprays H5,

H8, and H1 are selectively. rendered operz'ttive .t spray the water intothe tower at a level" wherein the temperature of the water correspondsto the wet bulb temperature. of the air rising. through the coolingtower I 8. If load con- 88 toprevent operation of the water vaporcompressor-21. 'This effectively prevents breakage of the water' vaporcompressor 21 which might be caused by water in a. liquid state enteringthe tower I8 above the-spray I82. Solenoid valves 7 same. p

The steam valve 54 which controls the supply of steam to the steamturbine 52 and hence which controls the evacuation of the relatively,cold

evaporator I1 and the temperature of the water to the level of the waterin the relatively cold evaporator I1. As the relative humidity of theair within the enclosure I increases the valve 54 is modulatingly openedand as the relative humidity decreases the valve 54-is modulating yclosed and for Purposes of illustration it is assumed that the humiditycontroller I48 maintains the relative humidity within the enclosurebetween 45% and 60%.- As the valve 54 is opened upon an increase inrelative humidity to lower the temperature of the after cooling coil I4the valve 15, is moved towards an open position a like amountto'increase the amount of sensible heat supplied to .the air passingover the reheat coil I5. Accordingly as the relative humidity increasesthe amount of latent cooling and the amount of sensibl heating areincreased whereby sensible heat is added to replace the latent heatremoved. With such an arrangementthe relative humidity of the air withinthe enclosure I8 may be eifectively regulated without disturbing to anygreat extent the dry bulb temperature conditions within the enclosureI8. The liquid levelcontroller I4I 'performs the same function as theliquid level controller I38,.nan'iely, stopping operation. of the steamturbine 52 and the centrifugal compressor 48 if the level of the waterin the evaporator I1 should rise to a value which would endanger thecentrifugal compressor 48.

The valves 58, 9|, and 92 which control the operation of spray 81, 88,and 85 are controlled by a temperature responsive controller I43connected by a capillary tube I44 to a bulb I45 responding to thetemperature of the water in the pipe 85. The valvesjll, SI, and 52 arealso re;-

action of the reheat coil I5. According y. the water-from the coolingtower which is utilized for reheat purposes dissipates heat to the airduring the reheating process whereby the temperature of this water islowered and this water at lower temperature is utilized for obtaininglower tem-4 cooling tower I8 a counter flow heat exchange est wate'robtainable with existing outside wet bulb temperatures. By reason of thecooling tower arrangement of this, invention a smaller tower with alesser amount of air flow there- 7 through may be utilized forperforming a predetermined amount of cooling therein.

Figure 2 is a diagrammatic illustration of the manner in which thetemperature responsive controllers- I and I31 and the liquidlevelresponsive controller I38 control the operation'of the motorized steamvalve 33. The motor of'the mospectively controlled by thermostat;- I;I41, and 7 I48, responsive to the wet bulb temperature of the air abovethe sprays 81, 88, and 85 respectively. The temperature responsivcontroller I43 and the thermostats I45, I41 and I48 oper te to pro.-

vide the above outlined sequence of operation,

namely admitting water to the cooling tower at a level wherein thetemperature of the water corresponds substantially to the wet bulbtemperature of the air rising through'the cooling tower I8.

The solenoid valves II8, II 3, and I28 are controlled by a temperatureresponsive controller I58 which is connected by a capillary tube I5I toa bulb I52 containing a volatile fluid and responsive to the temperatureof the water in the pipe H4. The valves H8, H5, and I28 arealsorespectively controlled by thermostats I53, I54,

' and I55 responsive to the wet bulb temperature of the air above thesprays II5, II5, and H1, respectively. The temperature, responsivecontroller I58 and the thermostats I53, I54, and I55 operate 7 to causethe water to be admitted to thecooling tower I8 at a point wherein thetemperature of the water and the wet bulb temperature of the air risingthrough the cooling tower I8 are-substantially the same.

It is here noted that the temperature of the precooling coil I3 ismaintained at a relatively high value so that it will performsubstantially.

torized steam valve 33 may be of the type shown and described in PatentNo. 2,028,110 granted to D. G. Taylor on January 14, 1936. Power-issupplied to the proportioning motor by line wires I58 and I5I leadingfrom some source of power (not shown) and the proportioning motor isprovided with-control terminals I52, I53, and I54. The oppositely actingrelay coils'and the balancing' potentiometer contained within theproportioning motor are connected across the control terminals I52 andI54 and the junction of the oppositely acting relay coils are connectedto the control terminal I53, v all as illustrated in the above referredto D." G. Taylor patent. When the external resistance across theterminals I52 and I53 becomes less thanthe external resistance across--the terminals I53 and I54 the valve 33 is moved towards an open positionand when the externalrosistance across the terminals I53 and I54 becomesless than the external resistanceacross the control terminals I52 andI53 the valve 33 is moved towards a closed position.

The temperature responsive controller I35 may comprise a bellows I55charged with a volatile fluid. for operating a lever I51 against theaction The lever of an adjustable tension spring I58. I51 in turnoperates aslider I 55 with respect to a resistance element I18 and forpurposes of illustration it is assumed that when thetemperature is 75,the slider I58 assumes an extreme right hand position'and as thetemperature increases to the slider v I5! is progressively moved to theleft until it assumes an extreme left hand positioni The temperatureresponsive controller I31 re-- sponsive to the temperature of the airleaving the precooling coil I3 may comprise a bellows I12 charged with avolatile fluid for operating a lever I13 against the action of anadjustable tension spring I14. The lever I13 operates a slider I15 withrespect to a resistance element I15 and for Purposes of illustration itis assumed that the slider I15 assumes an extreme left hand positionwhen the temperature is substantially 65 and is moved progressively tothe right as the temperature decreases to a value of 60 whereupon theslider I15 assumes an extreme ,right hand position.

The ,liquid level controller I38 may comprise-a pivoted lever I18operated by a float I19, The lever in turn operates a mercury switch I88provided with'electrodes I8I, I62, I83,and I84. When 10 the level of thewater in the evaporator chamber 28 is normal the electrodes I83 and I84are bridged but if the level of the water should become abnormally highthen the electrodes I8I and I82 are bridged.

The control terminal I62 is connected by wires I86 and I81 to the leftend of the resistance Y element I18 and the control terminal I64 isconnected by wires I88, I98 and I91 to the right end of the resistanceelement I18.- The control ter- 20 minal I64 is also connected by wiresI88 and I89 to the right end of the resistance element -I16. The controlterminal I63 is connected by a wire I 92 to the electrodes I82 and I83and the elec-' tro'de I84 is connected by wires I93 and I94 to theslider I 15. The left end of the resistance element I16 is connected bya wire I95 to' the slider I69. A resistance element I96 is connectedbetween wires I86 and I93 to counteract the effect of the resistance I16when the slider I15 is in the extreme left hand position as shown inFigure 2. The electrode I8I of the mercury switch I88 is connected bywires I91, I98, and I88 to the control terminal I64. 7 v

With the parts in the position shown it is seen that the resistanceelement I18 of the temperature responsive controller I36 is connectedacross the terminals I62 and I64 and that the slider I69 is connecteddirectly to the control terminal I63. Hence the motorized valve I33 isunder 40 the control of the temperature responsive controller I36 andsince the slider I69 thereof is in a mid-position the motorized valveI33 is likewise in a mid-position. As the temperature increases theslider I69 is moved towards the left .45 to movev the motorized valveI33 towards an open position and as the temperature decreases the sliderI69 is moved towards the right to move the valve 33 towards a closedposition. Accordingly the motorized valve 33 is modulatingly positionedbetween an open and closed position as the temperature within theenclosure I8 varies between 75 and 80 to maintain desired dry bulbtemperature condition within the enclosure I8. If now the temperature ofthe air leavin the precooling coil I3 should decrease below 65 theslider I15 of the temperature responsive controller I31 moves toward theright and in so doing it does two things, it gradually decreases theexternal resistance across the control terminals I63 and I64 to move themotorized valve 33 towards a closed position and it adds resistance inseries with the slider I69 oLthe temperature responsive controller I36to decrease the sensitivity thereof. Accordingly asthe temperatureleaving the precooling coil I3 decreases from 65 to 60 the motorizedvalve 33 is graduatingly positioned towards a closed position. In thismanner lowering of the temperature ofthe precooling coil I3 to a valuewhich would cause latent. 7 cooling. is effectively prevented. If thelevel of the water inthe evaporator chamber 28'should become abnormallyhigh a substantially complete. short circuit across the controlterminals I63 and I64 is completed and this circuit may be "some sourceof power (not shown).

traced from the control terminal I63 through wire I92, electrodes I82and I8! and wires I91, I98, and I88 back to the other control terminalI64. This causes complete closing movement of the motorized valve 33 tostop operation of .the water vapor compressor 46 whereby damage to thecompressor is .efiectively prevented. Figure 3 illustrates the manner inwhich the humidity responsive controller I48 and the liquid levelresponsive controller I controls the operation of the motorized steamvalve 54 and the motorized valve 16. Here again the motor ofthemotorized steam valve 54 may be of the type shown and described in theabove referred to D. G. Taylor patent and it is supplied with power fromline .wires 288 and 28I leading from The proportioning motor 54 isprovided with control terminals 282, 283, and 284 for controlling thedirection and extent of movement of the motoriz valve.

The humidity responsive controller I 48 may 4 comprise a hygroscopicelement 286 for operating a lever 281 against the action of anadiustable tension spring 288. The lever 281 in turn operates a slider289 with respect to a resistance element M8 and for purposes ofillustration it is assumed that when the relative humidity is'60% theslider 289 assumes an extreme left hand position and as the relativehumidity decreases from 60% to 45% the slider 289 is progressively movedto the right across the resistance element The liquid level responsivecontroller I may comprise a pivoted lever 2I2 operated by a float 2L3for operating a mercury switch 2 having electrodes 2I5, 2I6, 2H, and2I6. When the level of the water in the evaporator chamber-H is normalthe electrodes 2I5 and 2I6are bridged. The control terminal 282 'isconnected by a wire 228 to the left end of the resistance element 2I8'and the control terminal 284 is connected by wires 22I and 222 to theright end of the resistance element 2I8. The control terminal 283 isconnected by wire 223, electrodes 2" and 2| 8 and wire 224 to the slider289; The electrode 2I5 of the mercury switch 2I4 is connected by wires225 and 22I to the control terminal 284.

With the parts in the positions shown in Fig ure '3 the controlpotentiometer formed by the slider 289 and the resistance element 2I8 isconnected directly to the control terminals 282, .283, and 284 and sincethe slider 289 is in a midposition the motorized valve 54 is. in amid-pmh. tion. As the relative humidity increases the slider 289 ismoved to the left to graduatingly open the motorized valve 54 and as therelative humidity decreases the slider 289 is moved toward the right tograduatinglyclose themotorized valve 54. Accordingly the valve 54 ismodulatingly positioned in accordance with variations in relativehumidity within the .enclosure I8 to maintain the relative humiditywithin the enclosure I8 within predetermined limits, illustra-- tively60% and 45%. If the level of the water in the evaporator chamber 4Ishould become dangerously high the electrodes 2I5 and 6 are bridged tosubstantially short-circuit the control terminals 283 and 284 whereuponthe motorized valve 64 is moved to a closed position. This, as

pointed out above, effectively prevents damage to the centrifugalcompressor 48. a The motorized valve 54 operates a dual potentiometercontained within a suitable housing :21 and this dual potentiometer issuitably 10f line wires 23I and 232 leading from some source of power(not shown). The connections 8 76 so arranged that as the motorizedvalve 54 is I g'r'aduatingly opened and closed the motorized valve 16 isalso graduatingly opened and closed in like amounts. Hence as therelative humidity increases the valve 54 is opened to increase theevacuation of the relatively cold evaporator I1 of reheat performed bythe reheat coil I5 whereby the amount of dehumidification is increasedwithout materially affecting the dry bulb temperature within theenclosure I8.

Referring now to Figure 4 the temperature responsive controller I43which responds to the temperature of the water in the pipe 86'maycomprise a bellows 235 connected by the capillary tube I44 to the bulbI45 for operating a switch arm 236 against the action of an adjustabletension. spring 231. The switch arm 236 is adapted to progressively moveacross contacts 238, 239, and 248 and for purposes of illustration it isassumed that the switch arm 236 engages the contact 238 when thetemperature of the water is substantially 90, that it engages thecontact 238 when the temperature of the water is substantially 85, andthat it engages the contact 248 when the temperature of the water issubstantially 80.

The thermostat I46 may comprise a bellows 242 charged with a volatilefluid for operating a switch arm 243 against the action of an adjustabletension spring 244. The switch arm 243 is adapted to engage contacts245, 246, and 241,

and for purposes of illustration it is assumed that the switch arm 243engages the contact 245 at substantially 80, that it engages the contact246 at substantially 85, and that it engages the contact 241 atsubstantially 90. The structure of the thermostats I 41 and I48.is'exactly the same as that of the thermostat I46 and therefore likereference characters for like parts'have been utilized.

Power is supplied to the control system by means of line wires 258 and25I leading from some source of power (not shown), the line wire-and'245 of the thermostats I46, I41, and I48;

With the parts in the position shown in Figure 4 the temperature of thewater in the pipe 86 is substantially 90" and the wet bulb temperatureof the air rising through the tower I8 is substantially 90at a pointadjacent the thermostat I48. A circuit is thereupon completed from theline wire 258 through switch arm 236, contact 238, buss 254, contact 241and switch arm' 243 of the thermostat I48, wire 253, solenoid valve 82,and'wire 252 back to the other line wire 25I. Accordingly the solenoidvalve 82 is opened and the 90 water in the pipe 86 is disand the valve16 isopened to increase the amount perature adjacent the thermostat I46should be 90, then the solenoid valve 88 would open and the solenoidvalve 8| would close to render the spray 81 operative; If now due tofadecrease in cooling load the temperature-of the water in' the pipe 86should decrease to 85 and the temperature adjacent the thermostat I41should be '85, then the valve 8| would open whereby the spray wouldoperate to admit the 85 water at that point in the cooling tower wherethe wet bulb temperature of the air rising through the cooling tower issubstantially 85. If under these reduced load conditions the wet bulbtemperature adjacent the thermostat I48 should be 85, then the spray 88would be operated to spray the 85 water into the tower I8 or if the temvperature adjacent the thermostat I46 should be 85 then the spray 81would be operated to spray 85 water into the tower I8. The same sequenceof operation holds true ifthe temperature of the water in the pipe 86should be From the above it is seen'that the control system of Figure4operates at all times to'cause the water flowing through the pipe 86 tobe admitted into the cooling tower at a level wherein the temperature ofthe water is substantially the same as the wet bulb temperature of theair rising through the tower.

through the tower to perform the maximum amount or cooling at all times.To illustrate this point'a ssume that the temperature of-the water inthe pipe 86 is and that the wet bulb temperature or the air adjacent thespray 88 is 85. I

As the air rises through the tower it picks up heat from the wateremanating from the sprays and accordingly the wet bulb temperature ofthe air progressively increases as the air rises. The wet bulbtemperature of the air adjacent the spray 88 wil1 therefore be above 85and thewet bulb temperature of the air adjacent the spray 81.wi1ltherefore be below 85. The water falling from the sprays I82 and H5, H6or 1 is being cooled by the air and will assume values substantiallycorresponding to the wet bulb temperatures of the air at the variouslevels in the tower. If now the 85 water flowing through the pipe 86should be admitted to the tower through the spray 88, it will be coolerthan the wet bulb temperature of the air at this level. This water willtherefore absorb heat from the air' and accordingly it will be heated upwhich is just the opposite action to that cut short the cooling actionof the rising air on the water falling from the sprays I82 and I I5,'II8 or I I1. II on the other hand the-85 water is admitted to the towerthrough spray 81 then it will 7 This is an extremely important fea tureof this invention since it allows the air rising the after cooling coil264 by a relatively cold not be contacted by the rising air suflicientlylong to decrease the temperature thereof to the desired minimum.

If now the 85 water is admitted to the tower through spray 88 it willnot absorb heat from the rising air since the temperature thereof issubstantially the same as the wet bulb temperature of the air at thatlevel and it will allow the rising air to cool a maximum amount of thewater falling from the sprays I02 and H5, H6 or 1. Further' this waterwill contact the rising .,air sufficiently long to decrease thetemperaturethereof to the desired minimum. Accordingly the emciency ofthe cooling tower is greatly increased by this method of operation andsmaller cooling towers with a smaller flow of air therethrough may beutilized for accomplishing a predetermined amount of cooling. i

The wiring of the control system of Figure 4 may also be utilized forcontrolling the solenoid valves ,8, H9 and I inwthe upper part of thetower to admit water to the upper part of the tower at levels whereinthe temperature of the water corresponds to the wet bulb temperature ofthe air. Of course different temperature settings the air in the form ofa mist to the eliminator plates and. then drops down'through the .air inthe form of relatively heavy drops. A double cooling action by the airis therefore provided namely cooling the mist and cooling the drops.Accordin y, when the sprays H5, H6. and 1 are controlled in themannerpointed out above this double cooling action becomes morepronounced as the level at which .the water is admitted is lowered. Thissequence of operation therefore affords still greater economies in theoperation of thetower.

Summing up, by spraying water into thetower at levels corresponding tothe temperature of the water, that is by spraying the warmer water intotower at the'upper portion thereof and the cooler water into the towerat the lower portion thereof, a counterfiow heat exchange takes placebetween the water and the rising air which increases the efliciency'bfoperation of the cooling tower. By admitting the water into the tower atlevels wherein the temperature of the water corresponds to the wet bulbtemperature of the rising air, the efficiency of operation of the toweris further increased. Accordingly, with the tower arrangement of thisinvention -a maximum amount of cooling with a smaller tower and less airflow is made possible. p u

Figure 5 illustrates an arrangement wherein steam jet ejectors areutilized for cooling purposes instead of the steam driven centrifugal,compressors as in Figure l and also in Figure 5 a different controlarrangement is illustrated.

The enclosure to be air conditioned is designated at 266 and a fan 26ldraws air'through an air conditioning unit 262 and discharges condi-'tioned air into theenclosure 269. Either fresh "the air conditioningunit 262. 0001 water is supplied to the precpoling' coil 263 by arelatively warm evaporator 266, cold water is supplied to thetemperature of the water obtained in the evaporator chamber 219 issubstantially 60 evaporator 261 and water is supplied to the reheat coil265 by a cooling tower generally designated at 268. Here as in theprevious modiflcations, a counterflow heat exchange is afl'orded betweenthe air being conditioned and the water in the coils 263,264, and 265whereby the efllciency of the system is increased.

The relatively warm evaporator 266 may comprise a chamber 210 in whichcool water is collected and this cool water is drawn from the chamber210 through a pipe 21! by a pump 212 and is discharged through a pipe213, a motorized valve 214, and a pipe 215'to the precooling coil 263.For purposes of illustration it is assumed that the temperature of thewatersupplied to the 29! leading from somesource of steam (not shown)and the supply of steam is regulated by a motorized valve282. The steamjet ejector 280 discharges into a nozzle box 283 of a second ejector284. Water is supplied to the nozzles of the second ejector by a pipe285 and the water mixed with thesteam and air ejected from the ejector28!) is collected in a hot well 286. For purposes of illustration it isassumed that the temperature of the water entering the nozzles throughthe pipe 265 is substantially 85 so that Make. up water is supplied tothe evaporator chamber 210 by means of a water pipe 281 leading fromsome source of water (not shown) and prise an evaporator chamber 298 inwhich water is cooled and collected. A pump 292 withdraws cold waterfrom the evaporator chamber 299 through a pipe 29l and discharges thiscold water through a pipe 299 to the after cooling 'coil 264. Forpurposes of illustration it is assumed that the temperature of thiswater is substantially 50.' Water is discharged from the after coolingcoil 254 through a pipe 294, illustratively, at 60 into a spray 295located in the evaporator chamber 290, Part of the water sprayed out ofthe spray 295 evaporates to cool the remainder of the water. A conduit296 connects the evaporator chamber 299 to anozzle box 291 of a steamjet ejector 298. Steam is supplied to the nozzles in the nozzle box291'through a steam pipe 299 leading from some source of steam (notshown) and the supply of steam is regulated bya motorized valve 969. Thesteam jet ejector 296 disthe ejector 298 is condensed and iscollectedcharges into a nozzle box 8M of a second ejector 992 and water,illustratively, at "10 is supplied to the nozzles through a pipe 993. Byreason of this water it is possible to produce colder water (50) in theevaporator chamber 299 than in the evaporator chamber 219- The; 5mm fromalong with the water coming from the pipe 898- shown) and andthe air ina hot well 333, Make up water is supplied to the evaporator chamber 233by a pipe 305 leading from some source of water (not the supply of makeup water is controlled by a valve 336 which in turn is controlled by afloat 331 to maintain the level of the water in the evaporator chamber233 substantially constant. While steam valves 232 and 333 have been 7shown for controlling the evacuation of evaporators 266 and 261, theevacuation of theevaporators may. equally as well be regulated bycuttingin and cutting out in steps a plurality of steam jet ejectors andsuch is within the contemplation of this invention.

The cooling tower 268 may comprise a vertical chamber 3 I 3 providedadjacent its lower end with openings 3i I. A fan 3l2 draws air throughthe openings 3 and upwardly through the cooling tower to be dischargedto atmosphere. The air in passing upwardly through the cooling towercontacts water sprayed from a plurality of sprays for cooling the .waterand moisture is prevented from entering the fan 3l2 by means ofeliminator plates 313. Make up water is supplied to the cooling tower268 through a water pipe-3M leading from some source of water (notshown) and the supply of make up water is regulated by a valve 3|5 whichin turn is operated by a float 3 I 6 to maintain the level of the waterin the bottom of the cooling tower 268 substantially constant.

For-purposes of illustration it is assumed that V the water in thecooling tower is cooled to substantially 85 and this 85' water withdrawnfrom the cooling tower 263-throughapipe 323 by ,a pump 32! and isdischarged through pipes 322 and 285 into the nozzle box 283 of theejector of the relatively warm evaporator. By reason of this 85 waterthe temperature maintained in the evaporator. 266 is cooled toillustratively, 60.

- Water is withdrawn from the hot well 236 through a'pipe 323 by a pump.323 and this water is-discharged through a pipe 325 .into a spray 323located near the top of the cooling tower 263. For

v purposes of illustration it is assumed that the temperature of thewater entering the spray 326 is substantially lOO.

The pump 32l also supplies 85 water from the a temperahire responsivecontroller 333 responsiveto the temperature of the air leaving theprecooling coil 263 and for purposes of fllustration it is assumed thatthis temperature responsive controller in controlling the motorizedvalve 232 maintains the temperature of the air leaving the .preooolingcoil 263 between 60 .and 64". As the temperature increases the valve 232is moved towards an open position and as the temperature decreases thevalve 232 is moved towards a closed position. The motorized steam valveis also controlled by a temperature responsive controller I 353connected by a capillary tube 35] to a bulb 35,2 charged with a volatilefluid and responsive j to the temperature of the water in the pipe 213.

when the temperature of the water in'the pipe 8 213 is above 59, thetemperature responsive controller 333 controls the 'valve 232 but whenthe temperature of the water decreases below 59 the valve 232 is closed.

The motorized valve 333 controlling the operation of the relatively coldevaporator 261 is controlled by a temperature responsive controller 335responsive to the temperature of the air leaving the after cooling coil263 and this temperature responsive controller operatw to maintain thetemperature of the air at that point between substantially 59 and 62".As the temperature increases-the valve 333 is moved towards an openposition to decrease the temperature of the water J in the after coolingcoil-233 and as the temperacooling tower 268 through pipes322 and 321,

-.motorized valve 323, and'pipe 323 to the reheat coil 265 and water isdischarged from the reheat coil 265 at, illustratively, 70 through pipe333, motorized valve 33l, and pipe 333 into the nozzle box of theejector of the relatively cold evaporator 261. Water is withdrawn fromthe hot well 333 through a pipe.333 by a pump 333 and is dischargedthrough a pipe 335 intoone of a plurality of sprays 336, 331, and 333located in the-cooling'tower 263. For-purposes of illustration it isassumed that the temperature of this water is substantially 95. Theoperation of the sprays 336, 331, and 333 is controlled by solenoidvalves 333, 333, and= 3, respectively, and the purpose of these valvesis, as set out above. to admit the water at a level in the cooling tower263 wherein the water temperature corresponds to the wet bulbtemperature of the air rising through the cooling tower 263. If undersevere load conditions when all three solenoid valves 333, 333, and.3 3lshould be closed, then the pressure relief valve 332 opens to admit thewater to the spray 333. i

' the upper spray 333 or to spray 326 located above.

The motorized steam valve 232 is controlled by 15 ture decreases thevalve 333 is moved towards a closed position to increase the temperatureof the water in the after cooling coil. The temperature responsivecontroller 333 in addition to con? trolling the operation of the steamvalve 232 also controls the operation of the steam valve 333 to closethe steam valve 333' when the temperature of the air leaving theprecooling coil 263 decreases to substantially 60. -When the temperatureof the air leaving the precoolin coil 263 decreases to 60 there isreally no need for further cooling this air andtherefore the relativelyc'old evaporator 261 and the after cooling coil is rendered inoperative.The motorized valve'213 which regulates the rate of flow of coolingwater through the precoil 263 is'controlled by a temperature responsivecontroller. 333 responsive to thedry bulb temperature within theenclosure 263. As the temperature increases the valve 213 is movedtowards an open position to increase the rate oi flow whereby the air iscooled to a further extent bythe precooling coil. A s the temperaturewithin the enclosure decreases the valve 213 is moved towards a closedposition to throttle the flow of water through the precooling coil 263whereby the air is cooled a lesser extent. For purposes of illustrationit is assumed that the temperature responsive controller 336 operates tomaintain the dry bulb temperature within the enclosure 263 between 15and The motorized valve'323 which regulates the flow of water throughthe reheating coil .265 is controlled by a humidityresponsive'controller 331 responsive to the relative humidity within theenclosure 263. Upon an increase in relative humidity the valve 323 ismoved towards an open position to increase the amount of reheating ac- Ycomplished by the reheatcoil 265 and as the relative humidity decreasesthe valve 323 is moved towards a closed positionto decrease the amountof heating by reheat coil 265. By increasing the amount of reheating therelative humidity oi. the air discharged into the enclosure 233 isdecreased and the reforedesired relative humidity condiassaeaa j tionsare maintain'edwithin the enclosure 268.

For purposes of illustration it is assumed that the humidity responsivecontroller 341 operates to maintain the relative humidity conditionsbetween 45% and 60%.

The valve 33! controlling the flow of water from the reheat coil 265 tothe ejector of the relatively cold evaporator 261 is controlled by atemperature responsive controller 348 connected by a capillary tube 349to a bulb 350 responsive to the temperature of the water in the pipe330. Upon an increase in temperature of the water in the pipe 330 thevalve 33l is moved by the relatively cold evaporator would increase.

In response tothis increase in temperature of the water in the pipe 338the valve 33! is moved towards the closed position to slow down the rateof circulation in the water through the reheat coil 265 whereupon thewater is cooled to a greater extent which maintains the condensingtemperature at a relatively low value. For purposes of illustration, itis assumed that the temperature responsive controller 348 maintains thetemperature of the water in the pipe 330 between 60 and 70 so that waterin the relatively cold evaporator 261 maybe cooled to substantially 50.Valve 33I in effect acts as a limit control for valve 328 to preventfluctuation in enclosure relative humidity upon wide changes inenclosure dry bulb temperature.

Figure 6 illustrates the manner in which the motorized valves 282 and300 are controlled by the temperature responsive controllers 344 and345. The motorized valve 282 may be operated by a proportioning motorwhich may be of the to D. G. Taylor patent. Power is supplied to themotorized valve 282 by means of line wires 355 and 356 leading from somesource of power (not shown) and the motorized valve 282 may be providedwith control terminal 351, 358, and-359.

The temperature responsive controller 344 may comprise a bellows 368charged with a volatile fluid for operating a lever 36l against theaction of an adjustable tension spring 362. The lever 36! operates aslider 363 with respect to a resistance element 364. The lever 36I maybe provided with an extension 365 for operating a mercury switch 366having electrodes 361, 368,

I 369, and 316.- For purposes of illustration it is assumed that whenthe temperature of the air leaving the precooling coil 263 is at 64 theslider 363 is in the extreme right hand position and as the temperatureprogressively decreases, the slider 363 i moved progressively to theleft until such time as thetemperature decreases to 60 whereupon theslider 363 assumes an extreme left hand position. The electrodes 361 and368 of the mercury switch 366 are normally bridged I a lever 454 againstthe action of an adjustable tension spring 455. The lever in turnoperates a mercury switch 456 having electrodes 451, 458,

If I the temperature of the water should- 459, and 468. For purposes ofillustration it is assumed that the electrodes'459 and 468 are bridgedwhen the water temperature is above 59 and that the electrodes V451 and458 are bridged when the water temperature falls below'59.

The control terminal 351 is connected by wires 312 and 462 to the leftend of the resistance element 364, the control terminal 359 is connectedby a wire-313 to the right end of the resistance element 364, and thecontrol terminal 358 is connected by a wire 314 to the electrodes 458and 459. The electrode 460 is connected by a wire 463-150 the slider 363and the electrode 451 is connected by wires 464 and 312 to the controlterminal 351. With the .parts in the positype shown and-described in theabove referred tion shown in Figure 6 the slider 363 is in the extremeright hand position and the motorized valve 282 is wide open. As thetemperature decreases tomove the slider 363 towards the left themotorized valve 282 is progressively moved towards a closed position.Accordingly the motorized valve 282 is positioned in accordance with thetemperature of the air leaving the precooling coil 263. Ifthetemperature of the water in the pipe 213 should fall below 59", then theconnection between the control terminal 358 and the slider 363 is brokenand the control terminal 358 is connected through the electrodes 458 and451 to the control terminal 351. This closes the steam valve 282 toprevent the production of too cold water by the temperature responsivecontroller 344 if the thermostat 346 torized valve may. be provided withcontrol vterminals 318, 319, and 380 .for controlling the direction andextent of movement thereof.

The temperature responsive controller 345 may comprise a bellows 382charged with a volatile fluid for operating a lever 383 against theaction of an adjustable tension spring 384. The lever 383 operates aslider 385 with respect to a resistance element 386 an d' for purposesof illustration it is assumed that when the temperature of the airleaving the after cooling c0i1 264 is 62 the slider 385 is in theextreme right hand position as shown and as the temperature decreasesthe slider 385 is moved progressively to the left until such time as thetemperature decreases to 59 whereupon the slider 365 assumes an extremeleft hand position.

The control terminal 318 is connected by Wires 386 and 389'to the leftend of the resistance element 386 and the control terminal 380 isconnected by a wire 390 to the right end of the resistance element 386.The control terminal 319 is connected by a wire 3! to the electrodes 368and 369 of the mercury switch 366, the electrode 318 being connected bya wire 392 to the slider 385 and the electrode 310 being connected bywires 393 and 388 to the control terminal 318. With the parts in thepositions shown in Figure 6 the slider 385 is in an extreme right handposition and the motorized valve 300 is wide open. As the temperaturegradually decreases to move the slider 385 toward the left the motorizedvalve 308 is graduatingly positioned towards a closed position.Accordingly the motorized valve 300 is 402, 403, and 404.

, element 424 and for purposes of illustration that asrthe relativehumidity within 1 positioned in accordance with the position of theslider 385 as determined by the temperature of the air leaving the aftercooling coil 284. If now the temperature leaving the precooling coil 283should decrease to 60 the electrodes 318 and 388 are unbridged, and theelectrodes 369 and 310 are bridged which completes a-substantially shortcircuit across the terminals 318 and 319 to move the motorized valve 300to a closed position. This also interrupts control of the motorizedvalve 300 by the temperature responsive 4T controller 345. When thetemperature of the air leaving the precooling coil 283 risesabove 60..

say to 60%", the mercury switch 388 is tilted to the position shown inFigure 6 to place the motorized steam valve 300 under the control of thetemperature responsive controller 345.

Figure 7 illustrates the manner in whichthe motorized valve 214 iscontrolled by the temperature responsive controller 348. Here again themotorized valve may be operated by a proportioning motor of the typeshown and described in the above referred to D. G. Taylor patent andpower is supplied to this motor by means of line wires 400 and'401leading from some source of power (not shown). The motor is alsoprovided with control terminals 402, 403, and 404. The temperatureresponsive controller 348 may comprise a bellows 405 charged with avolatile fluid for operating a lever 408 against the action of anadjustable tension spring 401. The lever 406 operates a slider 408 withrespect to a resistance element 409 and for purposes of illustration itis assumed that the slider 408 sweepsprogressively from left to rightacross the resistance element 409 as the temperature of the enclosure280 increases from 75 to 80.

The control terminal 402 is connected by wire 410 to the left end of theresistance element 409 and the control terminal 404 is connected by wire411 to the right end of the resistance element 409. The control terminal403 is connected by wire 412 to the slider 408 wherebythe potentitheenclosure 280 increases from to the slider 423 is progressively movedfrom an extreme left position to an extreme right position.

The control terminal 411 is connected by wire 425 to the left end of theresistance element 424 and the control terminal 419 is connected by awire 425 to the right vend of the resistance element 424. The controlterminal 418 is connected by wire 421 to the slider 423. With the partsin .the position shown the slider 423 is in a midposition and hence thmotorized valve 328 is in a mid-position. As the relative humidityincreases the motorized valve 328 is graduatingly positioned towards anopen position and as the relative humidity decreases the motorized valveis graduatlngly positioned towards a closed position. Accordingly therelative humidity controller 341 modulatingly positions the motorizedvalve' 328 to regulate the flow of water through the reheatcoil 265 tomaintain the relative humidity in the enclosure 280 between 45% and 60%.

Figure 9 illustrates the manner in which the motorized valve 331 mayalso be operated by a proportioning' motor which may be ofthe type shownand described in the above referred to D. G. Taylor patent and power issupplied to the proportioning motor by means of wires 430 and 431leading from some source of power (not shown). provided with controlterminals 432, 433, and 434 for controlling the direction and extent ofmove-' ment of the motorized valve. The temperature responsivecontroller 348 may comprise a hellows 435 connected by the capillarytube 349 to the bulb 350 for operating'a lever 436 against the action ofan adjustable tension spring 431. The lever 436 operates a slider 438with respect to a resistance element 439 and for purposes ofillustration it is assumed that asthe temperature ofthe water in thepipe 330 increases from 60 to 70 the slider 438 is moved progressivelyfrom an I extreme left hand position to an extreme right hand position.

The control terminal 432 is connected by a wire 440 to the left end ofthe resistance element 438 and the control terminal 434 is connected bya wire 441 to the right'end of the resistance element 439. The controlterminal 433 is connected by a wire 442to the slider 438. With the partsin the position shown in Figure 9 the slider 438 is in a midition andhencev the motorized valve late the cooling eflect oi the p'recoolingcoil 283 which maintains desired temperature conditions 3 within theenclosure 280. a

Figure 8 illustrates the manner in which the motorized valve 328 isgraduatingly positioned by the relative humidity responsive controller341 responsive to the relative humidity within the enclosure 280. Themotorized valve 328 may be operated by a proportioning motor also of thetype shown and described in the above referred to D. G. Taylor patentand power is supplied to this proportioning motor by means of line wires415 and 418 leading from some source or power (not shown). Theproportioning motor is also provided with control terminals 411, 418,and 419. The relativehumidity responsive controller 341 may comprise ahygroscopic element 420 for operatins.:.a lever 422 against the actionof an adiustable tension spring 421. The lever 422 operates a slider 423with respect to a resistamii 331 is in a mid-position. As thetemperatureof the water increases the slider 438 is moved to the rightto move the valve 331 towards a closed position and as the temperaturedecreases the slider 438 is moved towards the left to move the motorizedvalve 331 towards an open position. Accordingly the motorized valve 331is positioned in accordance with the position of the slider .438 whichin turn is positioned in accordance with the temperature of the water inthe pipe 330. The temperature responsive controller 348 thereforemaintains the temperature of the water in the pipe 330 between 60 and 70so that relatively cold water may be produced in the relatively coldevaporator 281.

Figure 4 illustrates also the manner in which the solenoid valves 339,340, and 341 of the cooling tower 288 may be controlled to admit waterto the cooling tower at a level wherein the'temperature of the watercorresponds to the wet bulb temperature of the air rising through thecooling tower 288. As explained above, this greatly increases theefllciency of operation of the cool- Q The proportloning motor may alsobe lating air upwardly through the chamber, upper.

water For purposes 01' illustrationin this application,

various temperature values have been assumed but it is obvious thatthese values may be varie to suit different types of installations.

Although for purposes of illustration two forms of this invention havebeen disclosed other forms thereof may become apparent to those skilledin the art upon reference to this disclosure and' therefore thisinvention is to be limited only by the scope of the appended claims andprior art.

I claim as my invention:

1. In a cooling tower, the combination of, a substantiallyverticalchamber, means for circulating air upwardly through the chamber, upperand lower sprays in the chamber adapted to spray fluid in contact withthe circulating air whereby the fluid is cooled and the-air is heated,means for supplying fluid to the upper sprays from a source ofrelatively warm fluid, and'means for supplying fluid to the lower spraysfrom a source of relatively cool fluid, whereby a counterflow heatexchange between the air and the fluid is provided, said lower spraysincludingv a plurality of sprays spaced longitudinally in the chamber,and means for controlling the operation of the lower sprays to admitrelatively cool fluid there'- through at a level wherein the temperatureof the fluid corresponds substantially to the wet bulb temperature ofthe air.

2. In a cooling tower, the combination of, a substantially verticalchamber, means for circuand lower sprays in the chamber adapted to sprayfluid in contact with the circulating air whereby the fluidis cooled andthe air is heated, means for supplying fluid to the upper sprays from asource 01 relatively warm fluid, and means for supplying fluid to thelower sprays from a source of relatively'cool fluid, whereby a.counterflow heat exchange between the air and the fluid is provided,said lower sprays including a plurality of sprays spaced longitudinallyin the chamber, means for controlling the operation of the lower spraysto admit relatively cool fluid therethrough at a level wherein thetemperature of the fluid corresponds substantially to the wet bulbtemperature of the air, said upper sprays including a plurality oisprays spaced longitudinally inthe chamber, and means for controllingthe operation of the upper sprays to admit relatively warm fluidtherethrough at a level wherein the temperature of the fluid ccrrespondssubstantially to the wet bulb-temperature oi the air.

3. In a cooling tower, the combination of, a substantially verticalchamber, means for circulating air upwardly through the chamber, a pin-Irality 'of sprays spaced longitudinally in the 1. chamber adapted tospray a fluid in contact with the circulating air, and means forcontrolling the operation of the sprays to admit fluid through thesprays to the cooling tower at a level wherein the temperature of thefluid corresponds substantially to the wet bulb temperature of the air,said last mentioned means including means responsive to the temperatureof the air adjacent each spray.

4. In a cooling tower, the combination of, a substantially verticalchamber, means for circulating air upwardly through the, chamber, aplu-- ralityoi sprays spaced longitudinally in the chamber adapted tospray a fluid in contact with. thecirculating air, means for controllingthe operation of the sprays to admit fluid through the sprays to thecooling tower at a level wherein the temperature of the fluidcorresponds substan-' tially to the wet bulb temperature of the air,saidlastmentioned means including means responsive to the temperatureoi. the air adjacent each spray, and means responsive to the temperatureof the fluid.

5. In a cooling tower, the combination of, a substantially verticalchamber, means iorcirculating air upwardly through the chamber, aplurality of sprays spaced longitudinally in the chamber adapted tospray a fluid in contact with the'circulating air, means for controllingthe operation of the sprays to admit fluid through the sprays to thecooling tower at a level wherein the temperature of the fluidcorresponds substantially to the wet bulb temperature of the air, saidlast mentioned means comprising a valve controlling the flow of fluid toeach spray, a deviceadjacent each spray for sensing a temperaturecondition of the air, and a-thermostat responsive to the. temperature ofthe fluid, and means so relating said thermostat, devices, and valves sothat an individual device opens its respective valve when thetemperature adjacent that devicecorresponds' to the temperature of thefluid. I

6. In apparatus of the character described, in combination, meansforming a chamber having a gas therein, means for introducing a fluidinto the chamber at difierent levels, control means responsive to apsychrometric condition of the gas at said levels, the conditionnormally being difierent at the difierent levels, means responsive tothe temperature of the fluid, and means whereby the level at which fluidis admitted depends upon a predetermined relationship between the 'valueof the psychrometric condition of the gas at that level and thetemperature of the fluid.

ROBERT B. P. cRAwFoRn.

